The present invention, in some embodiments thereof, relates to flowing fluids on aerodynamic or hydrodynamic surfaces and, more particularly, but not exclusively, to flowing fluids on aerodynamic surfaces or hydrodynamic surfaces of a blade of a rotary machinery, such as helicopter or wind turbine.
Several methods are known in the art for actively manipulating fluid flow over a surface. One method widely used employs active flow control to increase turbulence, and more specifically certain relevant scales of turbulence, on the aerodynamic surfaces, for example by use of synthetic jet actuators.
For example, US 2007/0095987 to Glezer et al. discloses a synthetic jet actuator including a jet housing that incorporates an internal chamber with a volume of fluid and a small orifice in one dimension of the chamber connecting the internal chamber to an external environment having the fluid to be controlled. The synthetic jet actuator disclosed is operative to periodically change the volume within the internal chamber such that a synthetic jet stream entrained by a series of fluid vortices is generated and projected to the external environment.
US 2007/152104 to Cueman et al., for example discloses an array of synthetic jet actuators integrated in various applications, such as in aircraft engines or wings. Each actuator includes a chamber, a flow control port (a small orifice in one dimension of the chamber) and opposite parallel side walls configured to expand apart and contract together to flow a control fluid through the flow control port in response to an input.
Another example is described in U.S. Provisional Patent Application No. 61/288,386 filed on Dec. 21, 2009, which describes an oscillatory vorticity generator device for controlling the flow on an aero- or hydrodynamic surface of an element. The oscillatory vorticity generator device comprises two main walls, positioned opposite to each other, forming a first pair of walls and two other walls, the four walls each having proximal and distal ends, the distal ends connected to an aero- or hydrodynamic surface, a connection connecting the walls at their proximal ends, and an opening in the aero- or hydrodynamic surface, the opening being substantially contiguous with the two main walls and the two other walls.